DESCRIPTION (Applicant's Abstract): The overall goal of this research is to assess the utility of T2- and diffusion-weighted MR in aiding the clinical diagnosis of human stroke. At present, identification of stroke relies primarily on neurological assessment rather than physiological measurement, since the ability to study ischemic pathophysiology in humans has been limited. Rapid identification of all strokes represents a particularly difficult challenge. We believe that diffusion-sensitive MRI techniques can improve the management of stroke in these regions by noninvasively and rapidly providing diagnostic information that is not available from neurological assessments and that cannot be obtained by presently-used CT, conventional spin-echo, FLAIR T2, and single-shot diffusion-weighted MRI methods. We will focus on diffusion-weighted MR imaging (DWI) because of its inherent sensitivity to cellular energy failure and to cellular necrosis. During the first year of funding, we will test a battery of advanced DWI methods that build on single- and multi-shot spin-echo and echo-planar imaging (EPI) methods with presently-used and improved navigation for motion reduction. We will determine the optimal method based upon a composite index of signal-to-noise, resolution, scan time, and artifact minimization. This evaluation will be done by two blinded neuroradiologists on a population of 48 stroke patients. During the second and third years of funding, we will pursue our ultimate goal of improving diagnosis of stroke patients (n=96) by evaluating the performance of the optimal DWI method together with T2 to 1): depict the relevant lesion responsible for the clinical history and 2): better augment the neurological assessment than dose the conventional (T2-weighted) MR exam alone. We will test the hypotheses that DWI will identify acute lesions not seen with T2 at presentation, will identify acute lesions in patients with multiple ischemic lesions not readily differentiated by T2, and will predict the T2-weighted MR depiction of acute lesion at chronic timepoints and thereby eliminate the need for follow-up radiological studies. The successful completion of this work will provide objective criteria beyond the neurological exam and a rapid, non-invasive tool for the neurologist to improve the diagnosis and management of patients with acute stroke.